TianQin is a future space-based gravitational wave (GW) observatory targeting the frequency window of 10⁻⁴–1 Hz. A large variety of GW sources are expected in this frequency band, including the merger of massive black hole binaries, the inspiral of extreme/intermediate mass ratio systems, stellar-mass black hole binaries, Galactic compact binaries, and so on. TianQin will consist of three Earth orbiting satellites on nearly identical orbits with orbital radii of about 10⁵ km. The satellites will form a normal triangle constellation whose plane is nearly perpendicular to the ecliptic plane. The TianQin project has been progressing smoothly following the ‘0123’ technology roadmap. In step ‘0’, the TianQin laser ranging station has been constructed and it has successfully ranged to all the five retro-reflectors on the Moon. In step ‘1’, the drag-free control technology has been tested and demonstrated using the TianQin-1 satellite. In step ‘2’, the inter-satellite laser interferometry technology will be tested using the pair of TianQin-2 satellites. The TianQin-2 mission has been officially approved and the satellites will be launched around 2026. In step ‘3’, i.e. the TianQin-3 mission, three identical satellites will be launched around 2035 to form the space-based GW detector, TianQin, and to start GW detection in space.

The pollination during bees' foraging is vital to continue species on the Earth. However, the losses of bee colonies are being more extensive problems in recent decades, which have seriously impacted the global environment but have not received enough attention from human beings yet. Based on widely investigating detectable features, this article presents an IoT-based system for long-term and extensive monitoring of bee colonies. Multiple features, including temperature and humidity inside the hive, bee combs' weight, bee colony's sounds, and a number of bees passing through the hive entrance, can be detected hourly by the proposed system. Furthermore, a four-month practical monitoring indicates that the system can continuously operate without human intervention and the data can reveal the activity and growth of bee colonies. Especially, a swarming activity was successfully observed by the data, which shows a significant potential to recognize various activities of bee colonies. The highlights of this system are the capabilities of detecting diverse features, transmitting data wirelessly and that with a strong self-support ability. Because of these advantages, the system can operate for an exceeding long time without maintenance, which will largely benefit system deployment in the field. In the visible future, this system could contribute to the study of bee's behavior and the development of precision beekeeping.

TianQin is a Chinese space-based observatory concept with three drag-free spacecraft orbiting the earth to observe gravitational-waves in the millihertz range. Electrical charge is inevitably accumulating on its isolated test masses which are used as the mirrors for interferometers to measure gravity variation. Charge management system based on ultraviolet (UV) light is developed to reduce the charge-induced noises acting on the test mass in space gravitational experiments such as GP-B, LISA, LISA Pathfinder and TianQin mission. The UV LED is a new UV light source with some advantages relative to mercury lamps, such as smaller size, lighter weight, lower power consumption and higher efficiency. For these reasons, ground-based tests for the combination of UV LED and inertial sensor are essential. This paper presents the development of a charge management system based on a UV LED, its application to a torsion pendulum system with a TianQin-like test mass, and assesses the charge-management performance of the system. The experimental results indicate that the isolated test mass can be charged positively or negatively through UV illumination. It demonstrates that the charging and discharging rates can both reach higher than 10 ⁵ e s ⁻¹ , as well as spectral measurement of the pendulum charge resulting in a white noise level equivalent to ∼5 × 10 ⁵ e Hz ^{− 1/2} , satisfying the TianQin requirement.

Induction-based oil debris detection methods have shown a great potential for providing non-invasive monitoring and measurement to prolong the life of precise machinery. However, the superimposition of the induced voltages by the multiple debris particles prevents these methods from being more accurate. An artificial neural network is employed in this work to establish a general corrective framework aiming at solving the modeling and adaptability problems for different sensors, and a hybrid detection strategy is proposed to further reduce the detecting error under different aliasing conditions. A simulative test using two sinusoidal waveforms is conducted to validate the performance of the proposed method. Finally, an experiment is carried out with known oil debris concentrations ranging from 5 mg/L to 100 mg/L, and the linearity of the detected signals under the given concentrations is used to evaluate the performances of different methods. The results indicate that the maximum error by the proposed measurements is less than 20%, while for the non-corrected measurements, the maximum error is over 40%.

High-energy particles in space will inevitably penetrate the spacecraft into the suspended test mass, which would seriously affect the detection of gravitational waves; therefore, charge measurement and control are essential. Based on the working principle of space inertial sensors, this article proposes a new charge measurement scheme based on capacitive sensing in nonsensitive axes for simultaneous charge measurement during the detection of gravitational waves. According to the dynamic model and actual parameters, the resolution of the proposed method is evaluated as about $6.60\times 10^{-17}$ C in space, which can meet the detection requirement. Further, a torsion pendulum device was set up on ground to carry out charge measurement experiments and verify the evaluation method. The experimental results show that the optimal resolution with the capacitive sensing is about $1.65\times 10^{-14}$ C at 1 mHz, which agrees with the theoretical evaluation. This work demonstrates the feasibility of the capacitive sensing-based charge measurement, which will be a potential scheme in the detection of gravitational waves.